(a) Field of the Invention
The present invention relates to a method for preparing a cyclic olefin polymer and a cyclic olefin polymer prepared thereby, more particularly to a method for preparing a cyclic olefin polymer having a high bulk density and a cyclic olefin polymer prepared thereby.
(b) Description of the Related Art
Until now, inorganic materials such as silicon oxide or silicon nitride have been used in the field of information technology and electronics industry. As the need for compact and highly efficient devices increases, new materials having superior functionality are required. In this regard, polymers having a low dielectric constant and a low hygroscopy, superior metal adhesivity, rigidity, thermal stability and transparency, and a high glass transition temperature (Tg>250° C.) are drawing attention.
Such polymers may be used for insulating films of semiconductors or TFT-LCDs, protection films for polarizing panels, multichip modules, integrated circuits (IC), printed circuit board, molding compounds for electronics devices, optical materials for flat panel displays, etc.
For example, the cyclic olefin polymer, which is polymerized from a cyclic monomer such as norbornene, has better transparency, heat resistance and chemical resistance than the conventional olefinic polymers and very low birefringence and hygroscopy. Thus, it can be used for optical materials for CDs, DVDs and POF (plastic optical fiber), films for capacitors, low-dielectric IT materials, medicinal materials such as low hygroscopic syringes, blister packaging, etc.
Steam stripping has been employed as a method for obtaining a polymer having a high glass transition temperature. However, polymer obtained by this method has coarse and non-uniform particles. Also, it is difficult to dry the water added during the process and remove the monomer or the metallic catalyst. Moreover, the method is inefficient and consumes a lot of energy because a huge amount of steam has to be used.
U.S. Pat. No. 4,400,501 discloses a process of mixing a polymer solution and a non-solvent using a high shear stirrer to precipitate the polymer and filtering and drying the precipitated polymer. However, the polymer obtained by this process has irregular fluffy, fibery particles, whose bulk density being as low as 0.06–0.08 g/mL. Thus, a large amount of non-solvent should be used to discharge the slurry from the precipitation tank and transfer and wash it and drying is also inefficient because of low bulk density. So the productivity is very low.
U.S. Pat. No. 6,455,650 discloses a process of pouring a polymer solution into a non-solvent to precipitate the polymer and filtering and drying it. The polymer obtained by this process has irregular fluffy, fibery particles, whose bulk density is very low. Because the polymer solution has a small concentration, a large amount of solvent has to be used.
U.S. Pat. No. 4,414,386 discloses a process of mixing a non-solvent containing an alcohol and water with a polymer solution to precipitate the polymer. The polymer obtained by this process has somewhat long particles and the bulk density is increased to 0.16 g/mL. However, it is difficult to separate the water from the alcohol and the bulk density needs to be further improved.